Piston Ring Gaping for the 4G15 Mivec Rcolt Motor Rebuild

From the Mitsu Service Guide - 4G15 Mivec
Piston ring side clearance in ring groove mm  [LIMIT]
No. 1 0.03 − 0.07 [0.1]
No. 2 0.02 − 0.06 [0.1]





Measured all the pistons, used the small box to get them all at the same height



Use two wrist pins to square the piston ring in the bore






























Piston ring end gap mm
   No. 1 0.15 − 0.30 [0.8]
   No. 2 0.30 − 0.45 [0.8]
   Oil ring 0.20 − 0.50 [1.0]

Connecting rod big end thrust clearance mm
   0.10 − 0.25 [0.4]
Oil clearance at crankshaft pins mm
   0.025 − 0.040 [0.1]













CRANKSHAFT AND CYLINDER BLOCK
Crankshaft end play mm
   0.05 − 0.18 [0.25]
Oil clearance at crankshaft journals mm
   0.02 − 0.04 [0.1]
Cylinder block gasket surface warp mm
   0.05 [0.1]
Cylinder block gasket surface grinding limit (including cylinder head grinding amount) mm
   − [0.2]
Cylinder bore diameter mm
   75.50 − 75.53 [−]
Taper of cylinder mm
   0.01 or less [−]
Cylinder-to-piston clearance mm
   0.02 − 0.04

My Measurements of the Block

Bores Measurements

Averages	0.495	76.505	0.499	76.501	0.500	76.500	0.495	76.505
X is parallel to the crank				1 is 15mm from top deck
Y is 90degree rotation of the crank				2 is 2/3 down the bore
Pistons Diameter @ Skirt		76.42		76.42		76.42		76.42
Piston to Wall Clearance		0.080		0.075		0.075		0.080
Wiseco Recommended Clearance is		0.08889mm			Bore size	3.012	inches	76.5048	mm
OEM Piston to wall is		.02-.04	mm
Std OEM Piston Bore		75.5-75.53	mm
Deck		.05mm	std	0.1mm	limit
Top Ring Bore x		0.00500	inches	*Application - Street Moderate Turbo/Nitrous
Second Ring Bore x		0.00550	inchens	*Circle Track/Drag Race recommends .0055 & .0060
Therefore ring gap = [bore size (mm) / 25.4] * (ring bore)
Top Ring Gap		0.0150596	inches	0.382514	mm	0.015	inches rounded
Second Ring Gap		0.0165656	inches	0.420765	mm	0.016	inches rounded

We are running 3.5thou piston to wall clearance. Another friend went 4.5thou which isn't really needed due to the Wiseco composition.










































From the Mitsu Service Guide - 4G63
Install the piston ring into the cylinder bore. Force it down with a piston, its crown being in contact with the ring, to correctly position it at right angles to the cylinder wall. Then, measure the end gap with a feeler gauge. If the ring gap is excessive, replace the piston ring.

Standard value:
No. 1 0.25-0.40 mm (.0098-.0157 in.)
No.2 0.20-0.35 mm (.0079-.0138 in.)
Oil 0.20-0.70 mm (.0079-.0276 in.)
Limit:
No. 1, No.2 0.8 mm (.031 in.)
Oil 1.0 mm (.039 in.)